Landracing Forum
Tech Information => Aerodynamics => Topic started by: Bob Drury on March 14, 2014, 01:08:25 PM
-
If you go to http://www.dragracingonline/agent1320 there is a great shot of Alan Johnson's new Mopar Pro Stocker in a wind tunnel that shows amongst other things why you don't want a low scoop on the hood of a race car. The difference in low and high pressure air is quite evident and also shows why funny cars run such a high wickerbill to gain traction on asphalt. Bob
-
Assist, and thanks :cheers:
http://www.dragracingonline.com/agent1320/2014/1320-xvi_3-14.html
(http://www.dragracingonline.com/agent1320/2014/0313/Mopar-Dart-ProStock-side.jpg)
-
How come the guys in these tunnels never hold the smoke generator close to the floor?.
I want to see the air flow around the splitter. :-D
-
It's time for SSS to ask another one that many know, I'll betcha. What's a "wickerbill"?
-
Usually $5 to $10, depending on height.
-
...rim shot, please! :-D
-
Wicker bill is a Gurney lip. Across the Pond is is a definition of part of one's private parts (male)!
Thanks to the aforementioned Stan Beck who donates his issues of Automobile magazine to the home , this month's has the intro of the Dodge Dart featured.
Using a well worn phase, if that thing in the tunnel is a Dart, my Uncle's my Aunt!
-
Male private parts are one thing that I think I know -- but a Gurney Lip? You guys aren't helping me very much. Thanks for trying, though. . . :?
-
We would slide in different Gurney lips to balance speed with handling just before qualifying.
Hope that helps....... :-P
-
I`ll try Jon. On most serious race car rear wings there`s an L shaped lip across the trailing edge. It can usually be changed to vary the height and thus the airflow. This has a very noticible effect on the efficiency of the wing. The L shaped piece is a Gurney lip on this side of the pond or a wickerbill over `there`.
Pete
-
It got its name due to Dan Gurney's use of the technique to quickly tune the down force on a rear wing.
It is a small vertical lip at the trailing edge of a wing (hence the name lip) which significantly increased down force for a very small increase in drag.
It's primary advantage is that they can be engineered to be easily changed during a pit stop to increase down force or reduce it by simply sliding out one lip and inserting one of a different size.
It was a spur of the moment invention that revolutionized racing.
http://www.insideracingtechnology.com/Resources/gurneyflap.gif
http://allamericanracers.com/the-gurney-flap/
-
According to conventional wing wisdom it really should not work! :?
But this is what happens [sometimes] when you deal with hot rodders! :-o :-D :cheers:
-
“The purpose of science is to explain how hot rodders do what they do.” – Scott Guthrie (IIRC)
Mike
-
Using a well worn phase, if that thing in the tunnel is a Dart, my Uncle's my Aunt!
Just saw this thread!
IO.....ROTFLMFAO! :-D :cheers: :-D :cheers: :-D
Looks like NHRA is going/has gone the NASCRAP route!
Gregg
-
Here's a link to a Bangshift.com page that holds a video of a car that ran for the first time at SpeedWeek '13. Here it's tested in the A2 wind tunnel. If you were there you probably will recognise it. I didn't bother to create a new topic for it - that's why it's on this one.
http://bangshift.com/bangshift1320/watch-incredible-stupidbaker-land-speed-car-get-wind-tunnel-tested-a2-wind-tunnel/
I corrected my error - which Mr. Kitchen was kind enough to point out to me ( not to all of you). Thanks. :-)
-
I assume that drag force versus airspeed is measured during windtunnel testing. Are those numbers highly-guarded secrets for the StupidBaker?
-
WOW!!!
That is beautiful to watch. I sure hope someone gets the chance to put a stock bodied Stude in a wind tunnel in my lifetime.
It could answer a lot of Stude Aero questions that have been argued about since 1953! One Run, out...................
-
Jack: A couple of years ago, when the A2 tunnel was just getting up and running, one of the guys at the tunnel spent quite a bit of time here on the forum. Here told us lots of stuff about this-n-that, including that the data learned was exclusively for the team's use -- and not his to give out to anyone else. But - if the team gave him permission to disseminate the data he would/did do so.
He hasn't been on here for quite a while, so I will guess that we'll just have to assume that he's not going to comment on your expressed desire to find out more. Maybe the Stupidbaker's team will see this and offer something, though. If you know who they are -- ask 'em, hey?
-
Usually $5 to $10, depending on height.
Here Stan...I don`t need this any longer....www.instantrimshot.com
-
According to conventional wing wisdom it really should not work! :?
But this is what happens [sometimes] when you deal with hot rodders! :-o :-D :cheers:
A lot of research went into this in the 80's and 90's. If we put a Gurney flap on a wing trailing edge and then fair the upstream side we create an artifact called "trailing edge bluntness". It was actually pioneered in the 60's by Whitcomb. The drag of an airfoil is actually reduced by having a little of this depending on Reynolds number: the higher the Rn, the thicker the boundary layer is and the more bluntness works for us.
Essentially, it delays the closure of the airfoil trailing edge upper and lower boundary layers until farther aft of the physical trailing edge. So we get the benefit of an aerodynamically longer chord without the drag of longer chord, at the expense of some trim drag due to higher negative wing moment. It also can make for a lighter structure, and weight is everything for an aircraft. The most dramatic example currently is the G-650.
It takes pretty high end CFD to accurately model this effect and a lot tighter mesh than most people are willing to run. It's not magic, it is well known aero for 30-40 years that is in wide use.
As for un-faired Gurney flaps, they are in use on many small aircraft to stiffen the trailing edge of control surfaces. T shaped flaps on the rudder of many small aircraft prevent flutter and unload the control forces at minimal drag penalty. Conversely, many composite kit aircraft use way too much trailing edge bluntness because the bondo jockey who built it got lazy. For under 10M Rn, 0.5% chord is about right.
-
According to conventional wing wisdom it really should not work! :?
But this is what happens [sometimes] when you deal with hot rodders! :-o :-D :cheers:
A lot of research went into this in the 80's and 90's. If we put a Gurney flap on a wing trailing edge and then fair the upstream side we create an artifact called "trailing edge bluntness". It was actually pioneered in the 60's by Whitcomb. The drag of an airfoil is actually reduced by having a little of this depending on Reynolds number: the higher the Rn, the thicker the boundary layer is and the more bluntness works for us.
Essentially, it delays the closure of the airfoil trailing edge upper and lower boundary layers until farther aft of the physical trailing edge. So we get the benefit of an aerodynamically longer chord without the drag of longer chord, at the expense of some trim drag due to higher negative wing moment. It also can make for a lighter structure, and weight is everything for an aircraft. The most dramatic example currently is the G-650.
It takes pretty high end CFD to accurately model this effect and a lot tighter mesh than most people are willing to run. It's not magic, it is well known aero for 30-40 years that is in wide use.
As for un-faired Gurney flaps, they are in use on many small aircraft to stiffen the trailing edge of control surfaces. T shaped flaps on the rudder of many small aircraft prevent flutter and unload the control forces at minimal drag penalty. Conversely, many composite kit aircraft use way too much trailing edge bluntness because the bondo jockey who built it got lazy. For under 10M Rn, 0.5% chord is about right.
What he said.
How come the guys in these tunnels never hold the smoke generator close to the floor?.
I want to see the air flow around the splitter. :-D
That's normally because they do this in fixed ground tunnels with a taller than recommended boundary layer ;-)
-
How come the guys in these tunnels never hold the smoke generator close to the floor?.
I want to see the air flow around the splitter. :-D
That's normally because they do this in fixed ground tunnels with a taller than recommended boundary layer ;-)
[/quote]
I have no knowledge in this area, but I've always thought that it would be interesting to have a smoke wand out in front of a moving car, on the track. A car sitting still and its wheels not turning, has to be much different aerodynamically than a car moving down the track. I suppose it would be hard to achieve this, from a mechanical standpoint.
Either that, or someone needs to design a wind tunnel with a 500 mph floor! :-o
-
It shouldn't be hard at all-- simply mount a long tube sticking out in front of the car and pump smoke through it, letting the smoke flow back over the car as it travels forward.
Regards, Neil Tucson, AZ
-
That's why the Formula 1 guys all use Flo Viz paint. It's out there in the real world at speed. :-D :-D :-D
Pete
-
It shouldn't be hard at all-- simply mount a long tube sticking out in front of the car and pump smoke through it, letting the smoke flow back over the car as it travels forward.
Regards, Neil Tucson, AZ
There would be a lot of forces on that tube. I wonder if it's been done?
-
I always wondered why they don't have the smoke coming out of a manifold as wide as the vehicle?
JL222
-
I would think that the manifold running across the front would seriously affect the air flow.
Pete
-
...rim shot, please! :-D
www.instantrimshot.com You`re welcome
-
I seem to remember that there was a yellow stude back about 2006 that had about the same front end and it made too much down force and they had front tire trouble.
-
I would think that the manifold running across the front would seriously affect the air flow.
Pete
Pete;
I think the trick is to use streamline tubing for the manifold.
Regards, Neil Tucson, AZ